Projectile for multimissile ammunition



Oct. 23,

Filed Aug. 29, 1956 1962 E. N. HEGGE ETAL PROJECTILE FOR MULTIMISSILE AMMUNITION 2 Sheets-Sheet 1 EiEZL I3 JJJJJJJJJJJJJ'J JJJJJJJJJJJJJJ JJJJJJJJJJJJJU Lbbkk.

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LkLtM INVENTORS :Edwnrli .N Hag'ge Oct. 23, 1962 E. N. HEGGE ETAL 3,059,578

PROJECTILE FOR MULTIMISSILE AMMUNITION I EI- 2 Sheets-Sheet 2 Filed Aug. 29, 1956 .o c o oo .o o o 0 o o o g o o o INVENTORS E'. :'lwurd N Hagge BYTnhn TL McDonough W? Mo/0.0.@

nited States Patent O The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to multimissile ammunition for guns and is more particularly directed to multimissile projectiles wherein the dispersion pattern of the missiles is initiated subsequent to and independently of their emergence from the gun tube.

It frequently becomes necessary in modern warfare to spray a given area with a plurality of missiles in order to substantially increase the possibility of hitting one or more stationary or moving targets within that area. One of the methods for dispersing a plurality of missiles to increase the coverage of a given target area consists of explosively shattering a unitary projectile immediately prior to reaching the target. The effectiveness of such procedure, however, is severely limited by the fact that the majority of the projectile fragments are substantially diverted from their forward flight path so that only a relatively small portion thereof actually strikes the target area.

A far more eliicient method of striking a given target area with a plurality of missiles involves the use of ammunition comprising a plurality of missiles embedded in a suitable frangible matrix surrounded by a cylindrical metal casing commonly known as a canister which is adapted to be tired from a gun as a unitary projectile. Although canister ammunition has been successfully employed in smooth bore guns, the relatively low chamber pressures developed therein prohibit any substantial improvements in the velocity and range of the missiles. Accordingly, canister ammunition is now provided with a rotating band and is fired from rifled guns at high Velocities in an attempt to provide the relatively longer range and accuracy of fire demanded in present day warfare.

However, the use of canister ammunition at hypervelocities, i.e. at muzzle velocities of over 350() feet per second, introduces several factors which materially decrease the former effectiveness thereof. For one thing, the initial acceleration imparted to the canister projectile is so high that the resulting set-back movement of the missile filler therein frequently stresses the relatively thin metallic walls of the casing to the point of complete rupture. The resulting sharp, jagged edges which usually form along the line of break in the casing will, of course, effect severe galling and abrasion of the bore surfaces of the gin tube during the passage therethrough. Furthermore, in the event of severe rupture some of the missiles may escape from the casing and inflict serious peening damage to the rifling lands in the gun tube.

In fact, even if the casing were strong enough to resist rupture, the firing of conventional canister ammunition at relatively high velocities would still be ineffective in View of the poor dispersion patterns formed by the missiles during flight. Experiments have indicated that the unsymmetrical distribution of the missiles at the target area is primarily due to the longitudinal and radial movement thereof within the frangible matrix prior to the emergence of the casing from the gun tube. This premature looseness of the missiles is thought to be caused by the unavoidable large disparity between the powerful centrifugal forces imparted thereto by the rotation of the casing during passage through the rifled gun ICC tube and the relatively weak binding forces provided by the plastic matrix in which such missiles are embedded. These binding forces are kept at a relatively low level in order to permit the missiles to escape from the matrix with a minimum of interference. lnasmuch as the rilling lands impart an accelerating rotation to the casing, the missiles therein are subjected to a continuously increasing centrifugal force which produces a corresponding radial pressure on the interior bore surfaces of the casing. Such radial pressure often becomes great enough to force the relatively thin Walls of the casing outwardly into actual contact with the rifling lands in the gun tube. The resulting withdrawal of the peripheral support afforded to the embedded missiles by the casing permits the frangible binder material to break up and free the missiles for movement therein. During this expansion of the casing walls, the free missiles therein are so unevenly distributed by the radial and set-back forces imparted thereto that the subsequent liight pattern thereof is adversely affected.

While it may be possible to prevent the aforesaid premature movements of the missiles in the matrix in which they are embedded by reducing the frangibility thereof and increasing the strength of the material from which the casing is fabricated or, alternatively, increasing the wall thickness of the casing, the resulting delay in the complete release of the missiles therefrom subsequent to the emergence of the casing from the gun tube would be so great that the dispersion pattern would be relatively incomplete at the instant of striking the target area which in the case of conventional ball-type canister ammunition generally does not exceed a distance of 50 feet.

It is, therefore, an object of this invention to provide an improved multimissile projectile adapted to be fired from rifled gun tubes at muzzle velocities in excess of 3500 feet per second.

A further object of this invention is the provision of a multimissile projectile of such construction that the dispersion pattern thereof will be self-initiated subsequent to the emergence thereof from the gun.

Still another object of the present invention is to provide a multimissile projectile having self-contained means for controlling the extent and uniformity of the dispersion pattern thereof during the flight of the missiles toward the target area.

A still further object of this invention resides in the provision of an improved carrier construction for a multimissile projectile.

A specic object of this invention is to provide an improved round of canister ammunition adapted to be fired at chamber pressures in excess of 50,000 pounds per square inch.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a longitudinal crosssectional view of a multimissile projectile wherein the missiles are randomly packed in contiguous relationship in a matrix material having separate areas of different strength and toughness;

FIG. 2 is a transverse sectional View of a projectile similar to that of FIG. l but showing an arrangement wherein the missiles are symmetrically disposed in contiguous cylindrical layers in the interior of the projectile;

FIG. 3 is a cross-sectional view taken along the line 3 3 of FIG. 2;

FIG. 4 is a longitudinal cross-sectional view of a canister projectile wherein the missiles are symmetrically disposed in spaced apart relationship;

FIG. 5 is an enlarged transverse sectional View taken along the line 5 5 of PIG. 4;

FIG. 6 is a view showing a dispersion pattern formed on a 50efoot target by the missiles of a conventional canister round having a metal casing; and

FIG. 7 is a -view similar to that of FIG. 6 but showing the dispersion pattern formed on a similar 50-foot target by the missiles of the ammunition disclosed in FIGS. 4 and 5.

This invention resides in the means for controlling the dispersion patterns of multimissile ammunition and essentially comprises the concepts of embedding the missiles in a plastic binder in a pattern corresponding to the configuration desired at the target area, varying the strength level of the plastic binder at selected areas therein to release the missiles in the particular order required to achieve the desired dispersion pattern, and regulating the area of the dispersion pattern at the target by inclosing the missile binder in a thermosetting plastic adapted to assist in delaying the release of the missiles for a predetermined distance beyond the muzzle end of the gun tube.

As shown in the drawings, multimissile ammunition generally comprises a cylindrical outer casing 12 having a plurality of missiles 13 therein embedded in a binding matrix 14. While canister shot generally consist of steel balls which have been hardened to insure maximum penetration, it should -be understood that missiles 13 may take any projectile shape even to the extent of including stabilizing tins thereon in order to provide a substantial increase in the range at which the target may be located. Missiles 13 may be distributed at random throughout binding matrix 14 as shown in FIG. l or may be symmetrically stacked in uniform rows as best shown in FIGS. 2-5. The preferred arrangement, however, includes a plurality of tiers of missiles with each tier being formed by a centrally disposed missile surrounded by at least one ring of missiles. Since the tiers are uniformly stacked, the centrally disposed missiles form a longitudinal row coincident with the central axis of the binding matrix while the missiles in the surrounding ring form a plurality of longitudinal rows. If more than one ring of missiles is employed, the outer ring should be rotated relative to the adjacent inner ring so that each missile in the inner ring is disposed substantially between each pair of adjacent missiles in the outer ring. All the missiles in one tier may be contiguous to one another and, at the same time, the missiles in each tier may be contiguous to those in the adjacent tiers above and below as shown in FIGS. 2 and 3. On the other hand, the missiles and tiers may be in spaced relationship as shown in FIGS. 4 and 5. The latter arrangement makes it possible to vary the impact strength of the missile binder about the inner and outer rows of missiles for a purpose to be hereinafter explained.

The material of which the missile binder is formed must be sufficiently tough and elastic to resist and dampen the tendency of the missiles to move therein under the inertia and centrifugal forces imparted thereto during passage through the gun tube. However, such toughness must be limited in order to permit the ready release of the missiles 13 therefrom once the outer casing 12 has been discarded subsequent to the emergence thereof from the gun tube. In addition, the melting temperature of the matrix material 14 must be relatively low in order to facilitate the casting thereof into casing 12 about missiles 13 and, once poured, the molten plastic must have the ability to solidify uniformly upon cooling. It has been found that these properties are best provided by the thermosetting type of plastic material such as polyesters, epoxy resins, thiakols, or cornbinations thereof. If desired, a thermoplastic type of material such as a polyvinyl resin consisting of a combined chloride acetate in plastisol form may also be employed in view of the ease with which the toughness thereof can be varied. The preferred binder material, however, is of the polyester type.

In forming the round of ammunition shown in FIG. 1, the missiles are individually brushed with or dipped into a semisolid quantity of the matrix 14 and are then loaded at random into casing 12. The binder material employed for the rear half of matrix 14 as indicated at 15 is arranged to have a greater toughness than the material employed for the remaining forward portion 16 of matrix 14. The resulting projectile is thereafter placed in an oven and heated to a temperature of between 300 and 350 F. for a period up to a half hour in order to cure the binding material which solidities upon cooling to firmly hold the missiles therein. Once the casing material has been molded to the desired shape, it is able to resist temperatures well over 350 F. so that the curing of the matrix material 14 will have no effect thereon. Moreover, inasmuch as casing 12 and matrix 14 are each made of a different type of plastic material, there is very little or no surface afnity therebetween so that, any tendency for one material to stick to the other is virtually non-existent.

Ihe round of FIGS. 4 and 5 may `be formed by telescoping two or more hollow cylindrical molds of increasing diameters into a unit and then vfilling each cylinder with successive layers of binder materials 17, 18 and 19 in which missiles 13 are symmetrically embedded. The plastic material with which each mold is filled is selected so that the toughness thereof will decrease from the outermost to the innermost cylinder. This can be readily accomplished by varying the proportions of the constituents as, for example, the chloride and the acetate in the event thermoplastic material is employed. The missiles may be individually placed in each layer by suitable tongs or other instrument or may be merely dropped into place. The cylinders are not completely filled because of the necessity for leaving an exposed portion at the top thereof which can be utilized to pull each cylinder out from between the bands of plastic material. Inasmuch as each type of binder material is in a semisolid state, very little if any mixing therebetween will occur so that upon being cured, each cylindrical band will maintain its inherent toughness.

In the construction of FIGS. 2 and 3, the entire missile binder 14 is of the same type of plastic material throughout and is poured into a casing 20 in substantially the same measured quantities alternately with each layer of missiles.

Present day multimissile projectiles which are to be tired from a riiled gun are provided with a thin-walled metal casing having a rotating band of copper or other relatively soft metal fixed about the exterior thereof for receiving the rotational thrust imparted to the projectile by the riing bands in the gun tube. The casing is also frequently provided with a bourrelet which is an accurately machined steel band at the forward end portion of the casing to prevent contact thereof with the rifling bands in the gun tube. However, experiments have indicated that the attendant disadvantages of the metal casing, the rotating band, and the bourrelet can be entirely eliminated by fabricating the entire casing from a thermosetting plastic material. If desired, however, the rotating band can be made integral with casing 20 as shown at 21 in FIG. 3. Inasmuch as thermosetting plastic materials can be readily molded or machined to size, the casing can be made to the same diameter as the bore of the gun tube and thereby provide the functions of a rotating band as well as that of a bourrelet without the necessity of including separate components. Another important advantage offered by thermosetting plastics is the ability of the material to resist heat and to increase in rigidity and strength as the heat applied thereto is increased. This characteristic is utilized to eifect a material reduction in the frictional forces which normally retard the rotational velocity of the casing. During the initial engraving action between the steel rifling lands and the deformable exterior periphery of the casing considera-ble heat is generated by the frictional forces involved in the cutting of the rifling grooves. Inasmuch as the resistance of thermosetting plastic material to deformation increases in direct accordance with the amount of heat applied thereto, the rifling grooves become permanently set almost as soon as they are formed. The resulting decrease in the frictional forces produced `during the remainder of the passage of casing 12 through the gun tube actually increases the maximum muzzle velocity and rotational spin which can be imparted to the multimissile projectile thereby improving the accuracy of the individual missiles and at the same time increasing the maximum effective range thereof from the usual 50 feet to about 300` feet which, in the case of ball-type canister ammunition, is considered long range.

The most important characteristic of these thermosetting phenolics, insofar as multimissile ammunition is concerned, is their ability to provide a high impact strength under pressure without adversely affecting the required uniform disintegration thereof once the projectile has emerged from the muzzle of the gun tube. In the firing of multimissile ammunition from riiled gun tubes of calibers as large as 40 mm., chamber pressures up to 50,000 pounds per square inch are frequently encountered. In addition to these pressures, casing 12 is also subjected to inertia and centrifugal forces during the passage thereof through the gun tube. The combination of all these forces induces an extremely high rate of strain in casing 12 which as a result of the inherent characteristics of thermosetting plastic material produces Va drastic increase in the strength thereof during the continuance of the high strain rate therein. However, once casing 12 emerges from the gun tube, the consequent removal of the previous high rate of strain therein causes the thermosetting material to revert to its normal strength. Since such strength is below the forces imparted thereto during its rapid travel through the atmosphere, casing 12 will disintegrate accordingly. It has been determined that a high-impact type of phenolic plastic reinforced by the addition of a cord filler such as the residual scrap which accumulates during the manufacture of automobile tires can best withstand these high chamber pressures Without affecting the desired disintegration thereof upon emergence from the gun tube. For optimum results, however, the cords indicated at 22 should be of uniform length and distributed fairly evenly throughout the phenolic plastic as best shown in FIG. 3. The normal rupture strength of the casing is, of course, selected in accordance with the anticipated velocity thereof upon emergence from the gun tube. However, inasmuch as the impact forces which are imparted to a projectile after emergence thereof from a gun barrel generally reach a peak during passage through the relatively short blast area extending forwardly from the muzzle of the gun barrel, it is essential that the selected rupture strength of the casing material be low enough to permit initiation of the disintegration thereof during the interval of passage through the muzzle blast area. Although such requirement limits the degree of control which the strength of the casing material can exert over the ultimate dispersion of the missiles at the target area, the time required to complete the discarding of the casing from the missile binder can be varied to some extent by changing the proportion of the cord ller material in the thermosetting plastic material. The significant regulation of missile dispersion is actually achieved through the variation in the strength and toughness of the binder material. Thermosetting phenolics are additionally well-suited for use as the fabricating material for the casings of multimissile ammunition in view of the excellent dimensional stability and low moisture absorption characteristics as well as the ability to withstand long terms of storage and to function reliably under adverse climatic conditions.

Once the casing has disintegrated, the peripheral support given to the missile binder is removed thereby permitting the matrix or binder material to release the missiles therefrom under the high centrifugal forces imparted thereto. Sinc-e the rotational velocity of the multimissile projectile is but a small fraction of the forward velocity thereof, the slightest delay in the release of the missile from the binder material will result in a significant limitation on the degree of dispersion of the individual missiles. In the event the binding matrix is formed as shown in FIG. 1, the missiles in the forward half 16 will begin to disperse prior to those disposed in the rearward half 15. Thus, while the dispersement of the forward missiles will create alternate voids and concentrations due to the random disposition thereof, the subsequent release of the similarly disposed missiles in the rearward half will ll in and eliminate the voids which otherwise would exist in the coverage of the missiles over the target area. It is apparent that the different strength levels of binder material 14 need not be limited to the forward and rearward half of the cylindrical conguration thereof but may exist at a plurality of areas throughout in order to improve the uniformity of target coverage.

In the configuration shown in FIGS. 2-5, the central row of missiles is not subject to the centrifugal forces imparted to the outer rows and, therefore, will not disperse radially during ight except to the slight extent caused by the slight variations in the release of the missiles from the binder material. Inasmuch as the strength of the matrix material surrounding the central row of missiles as indicated at 19 is deliberately made weaker than the material 18 surrounding the inner ring of missiles, the central missiles will begin to move outwardly in matrix 14 prior to the surrounding missiles. Thus, the momentary delay of missiles 13 in the adjacent outer layer will serve to limit whatever radial movement may be imparted to the central row of missiles as a result of their misalignment with the central axis of the entire missile group. In the same way, the dilferences in strength of the matrix about the successive outer rings of missiles will serve to limit the dispersion of each inner ring. The dispersion of the outer ring of missiles, however, is only limited by the delay in their release from the binding material thereabout. Thus, upon impact with a target located at a distance of about 200-300 feet from the gun, the missiles will form a relatively compact group with a significant absence of voids and concentrations. If the strength of matrix 14 is successively decreased from the inner to the outer layers thereof, the dispersion of missiles 13 will, of course, be drastically increased but without the detrimental voids normally encountered with present day multimissile ammunition.

In the construction shown in FIGS. 4 and 5, the distance between the missiles in the irst inner ring and those in the central row produce an unavoidable lack lof coverage about the central portion of the target area. This can be remedied by placing the missiles in the first inner ring in contact with one another as well as in contact with the single missile in the center of the ring as shown in FIGS. 2 and 3. As a result, the radial movement imparted to the missiles in the first inner ring is limited in accordance with the length of the radius of the missile itself. As soon as matrix 14 is divested of casing 12, the missiles 13 therein begin to disperse radially. As a result, the release of each ring of missiles is delayed only by the extremely brief interval of time required for each missile to move from its original position to the exterior of the binder material. It is, therefore, readily apparent that the extent to which a group of missiles tired at high velocity from a riiled gun will disperse during the flight thereof toward a target area from 20G-300 feet away as well as the uniformity of such dispersion can be fairly closely controlled by embedding such missiles in a matrix of predetermined strength at selected levels or areas therein.

Thus, the employment of thermosetting plastics in the fabrication of canister ammunition in accordance with the concepts hereinbefore explained not only provides improved ballistic performance but also permits substantial reductions in the production costs thereof. The molding of a casing to the same `size as the bore of the gun is far less expensive than the fabrication of a metallic casing of smaller diameter than the bore which consequently requires the addition of a machined rotating band and 'bourreleL Further advantages of a cord-filled thermosetting plastic reside in the high heat resistance, low thermal conductivity and an impact strength which increases in direct correspondence to the rate of loading thereon. The uniform lengths of cord filler which are mixed with the thermosetting phenolic plastic not only increase the impact strength which can be attained but also serve to reduce the size of the fragments into which the casing will disintegrate subsequent to the emergence thereof from the gun tube. These advantages all contribute to rthe provision of effective and reliable canister ammunition which can be employed to `spray a given target area with a maximum amount of individual mssiles as best illustrated by the target of FIG. 7. Moreover, the ability to control the dispersion of the missiles is a highly desirable feature in the event the ring thereof is carried out by high velocity guns against targets located at longer ranges than heretofore possible with conventional canister ammunition. If the aforesaid control were not feasible, the dispersion of the missiles during the relatively long flight of between 200 to 300 feet would be so great that very few of the total missiles in the projectile would hit a target area of reasonable size.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised Within the spirit and .scope thereof and the following claims are intended to include such variations.

We claim: l

1. In a multimissile projectile adapted to be red from a rilled gun tube at any given muzzle velocity, a plurality of missiles, ya plastic binder material having `a different composition at selected areas thereof to provide corresponding predetermined levels of strength and toughness and in intimate contact with each of said missiles to form a unitary mass, and an outer casing of a thermosetting plastic intimately surrounding said unitary mass to serve as a carrier therefor during passage through the ried gun tube.

2. The combination defined in claim l wherein said thermosetting plastic includes a plurality of uniform lengths of cord material throughout.

3. In a multimissile projectile adapted to be red from a ried gun tube at a muzzle velocity in excess of 3500 lfeet per second, a plurality of spherical missiles, a thermosetting plastic binder material having a different composition at selected areas thereof to provide corresponding predetermined levels of strength and toughness and in intimate contact with each of said missiles to form a unitary cylindrical mass, said missiles being distributed throughout said binder material in accordance with the pattern desired at the target area and a one-piece outer casing of thermosetting plastic material having a plurality of uniform lengths of cord material throughout, said casing being in intimate engagement with the exterior periphery of said unitary mass to provide peripheral support thereto and ybeing of sulicient wall thickness to provide an interfering engagement with the riing in the gun tube whereby the resulting engraving act-ion therebetween imparts rotation to the entire projectile.

4. In a multimissile projectile adapted to be red `from a ried gun tube at a muzzle velocity in excess of 3500 feet per second, a cylindrical mass of thermoplastic binder material, a plurality of spherical missiles randomly distributed throughout said cylindrical mass, said binder `material being of lesser strength and toughness at the 8 forward end than at the rearward end thereof, and a one-piece outer casing of a homogeneous, cord-filled thermosetting plastic in intimate supporting engagement with the exterior periphery of said cylindrical mass of thermoplastic binder material, said casing being of sufcient wall thickness to engage the rifling in -the gun tube whereby the engraving action therebetween imparts rotational spin to the entire projectile during -the passage thereof through the gun tube.

5. In a multimissile projectile adapted to be red from a rilled gun tube at a muzzle velocity in excess of 3500 feet per second, a cylindrical mass of a thermosetting polyester binder material having a different composition at selected areas thereof to provide corresponding levels of strength and toughness, a plurality of spherical missiles symmetrically embedded in each of said strength and toughness levels of said binder lmaterial to form a series of tiers each comprising a central missile surrounded by at least one ring of missiles, and a one-piece outer casing of a homogeneous, cord-filled thermosetting phenolic compound in intimate supporting engagement with the exterior periphery of said binder material, said thermosetting phenolic plastic being highly resistant yto fracture only under the heat and compression imparted thereto dur-ing passage through the rifled gun tube.

6. The combination dened in claim 5 wherein each tier of missiles is separated from the adjacent tier and all the missiles in each tire are individually spaced apart from one another.

7. In canister ammunition adapted to be red from a titled gun tube at a muzzle velocity in excess of 3500 feet per second, the combination of a plurality of spherical missiles embedded in a thermoplastic matrix selected from one of the polyvinyl resins, said missiles being distributed in a series of tiers each comprising a central missile circumferentially surrounded by at least one ring of missiles, said matrix consisting of a plurality of concentric layers with the innermost thereof disposed to confine the centrally located missiles and each of said outer layers thereof disposed to conne one of said rings of missiles, each of said concentric layers being of different composition to provide corresponding varying levels of strength and toughness and a one-piece outer casing of a deforma-ble, cord-filled, thermosetting phenolic material in intimate supporting engagement with the exterior periphery of said outermost layer to serve as a carrier for said matrix during passage through the rifled gun tube whereby the continuous increase in lthe rate of loading on the thermosetting material converts the original deformability thereof to such frangibility that said casing releases said matrix therefrom upon emergence from the gun tube.

8. The combination defined in claim 7 wherein the composition of each of said layers provides a predetermined increase in the strength and the toughness thereof from the innermost to the outermost of said layers whereby the dispersion pattern of said missiles is controlled by the order in which release thereof from said layers is effected in response to the centrifugal force imparted thereto.

9. The combination defined in claim 7 wherein the composition of said thermosetting material provides a predetermined delay of relatively short duration in the release of said matrix from said casing for limiting the maximum dispersion pattern of said missiles.

10. In canister ammunition adapted to be tired from a riied gun tube at a muzzle velocity in excess of 3500 feet per second, the combination of a plurality of spherical missiles embedded in a thermosetting matrix selected from one of the polyesters, said missiles being distributed throughout said matrix in a series of spaced-apart uniform tiers each comprising a central missile circumferentially surrounded by at least one ring of missiles, said matrix consisting of a plurality of concentric cylindrical layers wherein the innermost thereof surrounds the centrally disposed missiles and each of the outer layers surrounds one of said rings of missiles, each of said concentric layers being formed of a different composition adapted to provide la predetermined strength and toughness for controlling the order in which said missiles are released from said matrix in response to the centrifugal force imparted thereto, and a one-piece outer casing of a deformable, cord-filled, thermosetting phenolic material in intimate supporting engagement with the exterior periphery of said outermost layer to serve as a carrier for said matrix during passage through the gun tube, said thermosetting material being of the type wherein the deformability thereof -is reduced in correspondence with the high rates of loading encountered during the passage thereof rthrough the gun tube whereupon said casing begins to release said matrix thereform upon emergence from the gun tube, the composition of said t-hermosetting l0 material being selected to provide a given rupture strength and thereby effect a predetermined delay of relatively short duration in the release of said matrix from said casing for limiting the maximum dispersion pattern of said missiles.

References Cited in the file of this patent UNITED STATES PATENTS 12,545 Davis Mar. 20, 1855 219,491 Mason Sept. 9, 1879 2,564,751 Cook Aug. 21, 1951 2,766,692 Mynes Oct. 16, 1956 2,820,412 Beeuwkes et al. Ian. 2l, 1958 FOREIGN PATENTS 7,169 Great Britain 1912 1,098,880 France Mar. 9, 1955 

